Fiber optic communication systems, where light is modulated and encoded (with desired information, such as voice, video or data) are transmitted via optical fibers.
One advantage of such optical fiber communication systems is the ability to transmit large amounts of information over a single optical fiber. However, as the number of users of such systems increases and as the quantity of data to be transmitted by each user also increases, it is necessary for a fiber optic communication system to accommodate the transmission of ever-greater quantities of information.
In some instances, it may be cost effective to deploy additional optical fibers, so as to increase the capacity of the fiber optic communication system. However, in many instances, it is extremely expensive to deploy new optical fibers and it is preferable to enhance the efficiency of channel utilization of enormous inherent bandwidth of the optical fibers in order to increase the quantity of information transmitted via a single optical fiber.
In dense wavelength division multiplexing (DWDM) systems, light having a plurality of different wavelengths is used. Each wavelength of light is independently modulated, so as to define a channel, which may be used to transmit information independently with respect to all other channels on the same optical fiber. Of course, the more independent channels which can be transmitted via a single optical fiber, the more the capacity of that optical fiber is to transmit information.
In order to increase the number of channels over which information can be transmitted via a single optical fiber, it is necessary to precisely control the wavelength of each channel. The wavelength demultiplexer and receiver of a fiber optic communication system can only demodulate and detect a channel efficiently when the wavelength of that channel is within a very narrow and predefined range. If the wavelength of the channel is outside of the predetermined wavelength range of the receiver, then the channel may be completely unusable.
Also, undesirable interference results when the wavelength of one channel drifts too close to the wavelength of an adjacent channel. The rate at which data is communicated in a channel must be decreased substantially in order to compensate for such interference. Thus, such interference inherently limits the spacing between channels and rate of cumulative transmission.
In view of the foregoing, it is desirable to precisely control the wavelength of each channel of an optical communication system, such as a dense wavelength division multiplexing (DWDM) fiber optic communication system. The market for precisely controlled wavelength locked laser modules is expected to be $0.5 billion dollars in 2010.
It is also desirable to package a semiconductor laser or laser array capable of providing a wide range of wavelengths along with a wavelength locker which assures desired choice of wavelength with stability over lifetime of a selected wavelength, within a contemporary hermetically sealed butterfly package.